No Baby Panda: Mom Was Faking Pregnancy

After months of waiting and hoping, panda lovers' dreams
were dashed again. There will be no baby panda at the National Zoo this year – mama bear was faking her pregnancy.

Zookeepers called off the pregnancy watch after noticing
that the prospective panda mother's hormone levels were back to normal, and that
there were no signs of a fetus during an ultrasound. Until now, the female had appeared
for all the world as if she was carrying a baby panda: She had elevated levels
of the hormone progesterone; she lost her appetite and slept a lot; and she even
built bamboo nests and cradled objects as if they were cubs.

Yet no one could be sure she was with-panda, because it is
often difficult to identify a panda fetus through an ultrasound. And female
giant pandas regularly undergo pseudo-pregnancies,
which mimic the real thing to a tee, sans the developing infant.

Repeat performance

This is the fifth time Mei Xiang (May Shee-ahng), one of two
giant pandas who live at the Smithsonian's National Zoo in Washington, D.C.,
has undergone a false pregnancy. She gave birth to one panda cub,
the male Tai Shan, in 2005. Zookeepers have been hoping for a repeat
performance since then, and inseminated her again this year with sperm from her
male companion at the zoo, Tian Tian (T-yen T-yen).

Pandas only have one shot to
get pregnant every year – females can ovulate once a year, and are fertile
for about two days. After that, the resulting pregnancy – or pseudo-pregnancy –
generally lasts between three to six months.

Scientists don't know why pseudo-pregnancies happen, or if
they have evolved for an evolutionary purpose.

"In a sense there's no answer, but there is speculation
that perhaps pandas' bodies just rehearse pregnancy all the time," Lisa
Stevens, curator of primates and pandas at the zoo, told LiveScience.

In the case of pandas, she said, some researchers think the
phenomenon could be related to the fact that the bears have evolved to survive on
a very low-energy diet. They eat almost nothing but bamboo, which contains
barely more energy than it takes to consume it.

But giant
pandas aren't the only ones that experience false pregnancies. Many
animals, especially carnivores and other bears, can go through the same thing.
Even humans can have symptoms associated with a pregnancy, without carrying an
actual baby. It's just that in most species, especially humans, it's easier to
tell for sure with an ultrasound.

Clara has a bachelor's degree in astronomy and physics from Wesleyan University, and a graduate certificate in science writing from the University of California, Santa Cruz. She has written for both Space.com and Live Science.